The invention relates to a luminaire comprising:
a housing with a light emission window in a plane P; PA1 a tubular electric lamp having a longitudinal axis, in the housing; PA1 concave reflectors which extend to inside the light emission window, laterally of the lamp in the housing, PA1 which reflectors are curved, while the lamp is positioned between the reflectors so as to throw light radiated transversely to the longitudinal axis through the light emission window to the exterior at an angle to plane P greater than a cut-off angle .beta.; PA1 a plurality of concavely curved slats which are V-shaped in cross-section, which extend transversely to the reflectors, which extend to inside the light emission window, and which each have between the reflectors a reflecting inner surface facing the lamp, which inner surface has flanks which extend from a central zone, centrally between the reflectors, at an angle away from the plane P. PA1 that the end zones of the inner surface of each slat may be mirrors which image the upper portion of the lamp, i.e. the portion facing away from the light emission window; and PA1 that the image of the upper portion of the lamp may coincide with the lower portion of the lamp, i.e. the portion facing the light emission window, and may overlap said lower portion more than entirely or only partly; and PA1 that no bright spots are visible within the cut-off angle if the image coincides with the lower portion of the lamp, and also if the image overlaps this lower portion only partly. These recognitions will be explained with reference to the drawings.
Such a luminaire is known from WO-A-96/25 623 to which U.S. Pat. No. 5,758,954 corresponds.
The slats of the known luminaire each have a reflecting inner surface which is to prevent that much light, for example approximately 10%, is intercepted by the slats and is largely lost in the slats, as would be the case if the slats were open, or is absorbed as would be the case if the slats had a light-absorbing inner surface
The inner surface of each slat extends from a zone centrally between the reflectors along its flanks at an angle upwards up to the reflectors in order to prevent undesirable reflections. It is in fact known from EP-A-0 122 972 that, if a light beam hits the inner surface just before it would reach a reflector in the case of slats having reflecting, for example mirroring inner surfaces parallel to plane P, this light beam would be reflected by the inner surface in such a direction that very bright spots are visible from the cut-off angle. Although the reflectors are only designed to throw light coming from above, directly from the lamp, to the exterior outside the cut-off angle .beta., the light reflected on the inner surface reaches the reflector from below. The inner surface and the reflector together can accordingly display very bright images of longitudinal portions of the lamp within angle .beta. which constitute glare.
The fact that the inner surface rises towards the reflectors in its flanks outside a central zone achieves that the inner surface reflects the incident light to locations higher up in the housing which are designed for dealing with light which comes to a greater or lesser extent from below. The light reflected by the inner surface is as a result utilized after a subsequent reflection and added to the light beam formed by the luminaire.
The slats extend to above the lamp in the luminaire according to the cited EP-A-0 122 972. The zone of the inner surface positioned centrally between the reflectors in this luminaire may be straight and parallel to plane P, or cylindrical and parallel to the lamp. The inner surface of each slat in this luminaire has lateral edges which extend transversely to the longitudinal axis of the lamp and which are mutually parallel.
The slats also extend to above the lamp in the luminaire known from DE-A-32 15 026. The inner surface of each slat is substantially closed and reflecting. The lateral edges of the inner surface, however, approach one another in a direction from the central zone towards the reflectors.
This is also the case in the luminaire known from US-A-4,888,668. The lateral edges of the inner surface, however, here approach one another so strongly that they already reach one another in a point of intersection at a distance from the reflectors. The upper side of the slat extends from the point of intersection parallel to plane P towards the reflectors. The slat does have a small thickness of approximately twice the thickness of the slat material in this location at its upper side, but the slat has a comparatively small height there. It still lies below the longitudinal axis of the lamp. The slat is irradiated by the lamp there and can still cause bright spots within the cut-off angle through reflection on the reflectors.
It is a disadvantage in a luminaire having only one light emission window, such as the luminaire of the cited DE-A-32 15 026 and of the cited US-A-4,888,668, that the lateral edges of the inner surface approach one another, because this is a result of the presence of flat side surfaces approaching one another in upward direction. These give rise to additional reflections in the luminaire and thus to additional light losses.
It is an important disadvantage, however, that slats may be comparatively voluminous owing to the rising inner surface and accordingly require comparatively much material, for example synthetic resin or metal, for example metal plating, if the slats extend up to a comparatively large distance away from the light emission window. This may be the case, for example, owing to a comparatively great dimension of the light emission window transverse to the longitudinal axis, or owing to the shape of the reflectors such that these are still comparatively far removed from one another comparatively high in the housing, or owing to a comparatively great angle at which the inner surface extends in a direction away from plane P.
It is known from NL-A-94 02 049 to give the inner surface a stepped shape, so that the slats in lateral view have an inner surface with a sawtooth contour. This renders the slats less voluminous. The slats, however, have a complicated shape which is difficult to manufacture.